Polymer damped tubular shafts

Abstract

A golf club shaft including a damping layer which serves to reduce the amplitude of vibrational waves subject upon a golf club shaft is provided. The damping layer which includes, at least in part, an elastomeric material is coated to the inner diameter of the golf club shaft along a desired length. A method is also provided which relates to reducing the effects of induced modes of vibration upon a golf club shaft.

We claim: 
     
       1. A golf club shaft, which is attached along one end to a club head and along a second end accommodates a grip, said shaft being susceptible to multiple frequency modes of vibration upon said club head contacting a golf ball, said golf club shaft comprising: a hollow elongated sleeve having an inner surface and an outer surface; and   an elastomeric damping layer formed from a coating material applied directly to said inner surface of said sleeve along a selected length thereof;   whereby said damping layer effects a reduction in any extentional vibration wave transmitted along the shaft.   
     
     
       2. The golf club shaft of claim 1, wherein said elastomeric damping layer has a Shore A durometer hardness of between about 30 to about 70. 
     
     
       3. The golf club shaft of claim 2, wherein said elastomeric damping layer has a density of between about 0.5 g/cm 3  to about 2.5 g/cm 3 . 
     
     
       4. The golf club shaft of claim 3, wherein said elastomeric damping layer has a substantially even thickness. 
     
     
       5. The golf club shaft of claim 4, wherein said substantially even thickness includes an average thickness of less than about 0.35 inch. 
     
     
       6. The golf club shaft of claim 3, wherein said elastomeric damping layer has a substantially uneven thickness. 
     
     
       7. The golf club shaft of claim 6, wherein said uneven thickness includes intermittent portions having an enhanced thickness. 
     
     
       8. The golf club shaft as in any of the preceding claims, further comprising a second layer of polymeric material disposed over said elastomeric damping layer, said layer of polymeric material having a hardness upon curing equal to or greater than said elastomeric layer. 
     
     
       9. A method for reducing the amplitude of induced modes of vibration upon a hollow metallic golf club shaft including an inner and outer surface, comprising the steps of: rotating said shaft at a relatively constant rate of speed;   applying a liquid mist including elastomeric material to a selected length of said inner surface while said shaft is being rotated; and   curing said elastomeric material by subjecting the golf club shaft including the elastomeric material to heat at elevated temperatures;   whereby upon curing said elastomeric material, a damping layer is provided along a selected length of the inner surface of said shaft, said damping layer effectively reducing any extentional vibration waves transmitted along the shaft.   
     
     
       10. The method according to claim 9, wherein the step of curing said elastomeric material involves the step of placing said shaft in contact with an induction coil. 
     
     
       11. The method according to claim 9 comprising the further step of applying a layer of polymeric material over said layer of elastomeric material. 
     
     
       12. A golf club shaft comprising: a hollow elongated sleeve having an inner surface and an outer surface;   an elastomeric damping layer formed from a coating material applied directly to a selected length of said inner surface of said sleeve; and   a layer of polymeric material applied over said elastomeric damping layer, said layer of polymeric material having a hardness upon curing equal to or greater than said elastomeric damping layer.   
     
     
       13. The golf club shaft of claim 12, wherein said elastomeric damping layer has a density of between about 0.5 g/cm 3  to about 2.5 g/cm 3 . 
     
     
       14. The golf club shaft of claim 13, wherein said elastomeric damping layer has a substantially even thickness. 
     
     
       15. The golf club shaft of claim 14, wherein said substantially even thickness includes an average thickness of less than about 0.35 inch. 
     
     
       16. The golf club shaft of claim 14, wherein said elastomeric damping layer has a substantially uneven thickness. 
     
     
       17. The golf club shaft of claim 16, wherein said uneven thickness includes intermittent portions having an enhanced thickness.